The IceCube Neutrino Observatory at the South Pole has measured astrophysical neutrinos using through-going and starting events in the TeV to PeV energy range. The origin of these astrophysical neutrinos is still largely unresolved, and among their potential sources could be dark matter decay. Measurements of the astrophysical flux using muon neutrinos are in slight tension with starting event measurements. This tension is driven by an excess observed in the energy range of 40-200 TeV with respect to the through-going expectation. Previous works have considered the possibility that this excess may be due to heavy dark matter decay and have placed constraints using gamma-ray and neutrino data. However, these constraints are not without caveats since they rely on the modeling of the astrophysical neutrino flux and the sources of gamma-ray emission. In this work, we derive background-agnostic galactic and extragalactic constraints on decaying dark matter by considering Tibet AS$_γ$ data, Fermi-LAT diffuse data, and the IceCube high-energy starting event sample. For the gamma-ray limits, we investigate the uncertainties on secondary emission from electromagnetic cascades during propagation arising from the unknown intensity of the extragalactic background light. We find that such uncertainties amount to a variation of up to $\sim 55\%$ in the gamma-ray limits derived with extragalactic data. Our results imply that a significant fraction of the astrophysical neutrino flux could be due to dark matter and that ruling it out depends on the assumptions on the gamma-ray and neutrino background. The latter depends on the yet unidentified sources.
We review the prospects for detecting quark matter in neutron star cores. We survey the proposed signatures and emphasize the importance of data from neutron star mergers, which provide access to dynamical properties that operate on short timescales that are not probed by other neutron star observables.
We discuss likely sources of cosmic rays in the $10^{15}-10^{20}$ eV range and their possible very high energy neutrino and gamma-ray signatures which could serve to identify these sources and constrain their physics. Among these sources we discuss in particular low luminosity gamma-ray bursts, including choked and shock-breakout objects, tidal disruption events and white dwarf mergers. Among efforts aimed at simultaneous secondary multi-messenger detections we discuss the AMON program.
Supermassive black hole binaries (SMBHBs) are a natural outcome of galaxy mergers and should form frequently in galactic nuclei. Sub-parsec binaries can be identified from their bright electromagnetic emission, e.g., Active Galactic Nuclei (AGN) with Doppler shifted broad emission lines or AGN with periodic variability, as well as from the emission of strong gravitational radiation. The most massive binaries (with total mass >10^8 M_sol) emit in the nanohertz band and are targeted by Pulsar Timing Arrays (PTAs). Here we examine the synergy between electromagnetic and gravitational wave signatu…
The origin of neutrino flux observed in IceCube is still mainly unknown. Typically two flux components are assumed, namely: atmospheric neutrinos and an unknown astrophysical term. In principle the latter could also contain a top-down contribution coming for example from decaying dark matter. In this case one should also expect prompt and secondary gammas as well. This leads to the possibility of a multimessenger analysis based on the simultaneous comparison of the Dark Matter hypothesis both with neutrino and high energy gamma rays data. In this paper, we analyze, for different decaying Dark …
Clear methods to differentiate between decaying and annihilating dark matter (DM) scenarios are still by and large unavailable. In this note, we study the potential astrophysical signatures of a new class of hidden sector decaying DM models, which can address the recent cosmic ray measurements. Such models may produce primary photons and/or neutrinos at large rates, correlated with the leptonic production. The photon and neutrino spectra will then contain sharp features at the TeV scale. We demonstrate the discovery potential for upcoming and future measurements by FERMI, HESS, AGIS and IceCub…
If dark matter decays into electrons and positrons, it can affect Galactic radio emissions and the local cosmic ray fluxes. We propose a new, more general analysis of constraints on dark matter. The constraints can be obtained for any decaying dark matter model by convolving the specific dark matter decay spectrum with a response function. We derive this response function from full-sky radio surveys at 408 MHz, 1.42 GHz and 23 GHz, as well as from the positron flux recently reported by PAMELA. We discuss the influence of astrophysical uncertainties on the response function, such as from propag…
Up to date, there is no consensus regarding the origin of ultra-high energy cosmic rays (UHECR) beyond the Greisen--Zatsepin--Kuzmin (GZK) limit. In order for these UHECRs to reach the Earth, an extremely suppressed interaction between them and the cosmic microwave background (CMB) is required, which is impossible for standard model (SM) particles, except neutrinos. In this letter, we present constraints on the parameter space of models involving axion-like particles and dark photons, as candidates for UHECRs, by assuming that these particles can traverse the visible Universe without decaying.…
Decaying dark matter has previously been proposed as a possible explanation for the excess high energy cosmic ray electrons and positrons seen by PAMELA and the Fermi Gamma-Ray Space Telescope (FGST). To accommodate these signals however, the decays must be predominantly leptonic, to muons or taus, and therefore produce neutrinos, potentially detectable with the IceCube neutrino observatory. We find that, with five years of data, IceCube (supplemented by DeepCore) will be able to significantly constrain the relevant parameter space of decaying dark matter, and may even be capable of discoverin…
The gravitational collapse of rapidly rotating massive stars can lead to the onset of the low $T/\|W\|$ instability within the central proto-neutron star (PNS), which leaves strong signatures in both the gravitational wave (GW) and neutrino emission. Strong large-scale magnetic fields are usually invoked to explain outstanding stellar explosions of rapidly rotating progenitors, but their impact on the growth of such instability has not yet been cleared. We analyze a series of three-dimensional magnetohydrodynamic models to characterize the effects of different magnetic configurations on the de…
In this Letter, we study the gamma-ray signatures subsequent to the production of a Higgs boson in space by dark matter annihilations. We investigate the cases where the Higgs boson is produced at rest or slightly boosted and show that such configurations can produce characteristic bumps in the gamma-ray data. These results are relevant in the case of the Standard Model-like Higgs boson provided that the dark matter mass is about 63 GeV, 109 GeV or 126 GeV, but can be generalised to any other Higgs boson masses. Here, we point out that it may be worth looking for a 63 GeV line since it could b…
We set conservative constraints on decaying dark matter particles with masses spanning a very wide range ($10^4-10^{16}$ GeV). For this we use multimessenger observations of cosmic-ray (CR) protons/antiprotons, electrons/positrons, neutrinos/antineutrinos and gamma rays. Focusing on decays into the $\bar{b}b$ channel, we simulate the spectra of dark matter yields by using the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equations and the $\texttt{Pythia}$ package. We then propagate the CRs of dark matter origin till Earth by using the state-of-the-art numerical frameworks $\texttt{CRPropa}$, $\t…
The origin of dark matter is a driving question of modern physics. Low-energy antideuterons provide a "smoking gun" signature of dark matter annihilation or decay, essentially free of astrophysical background. Low-energy antiprotons are a vital partner for this analysis, and low-energy antihelium could provide further discovery space for new physics. In the coming decade, AMS-02 will continue accumulating the large statistics and systematic understanding necessary for it to probe rare antinuclei signatures, and GAPS, which is the first experiment optimized specifically for low-energy cosmic an…
Multi-messenger signal from QCD-Axion Ultracompact Minihalos
Institut de Fìsica d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology（高能物理研究所，巴塞罗那科技研究院）；Facultad de Ingeniería, Universidad San Sebastián（圣塞巴斯蒂安大学工程学院）；Departamento de Ciencias Físicas, Universidad Andrés Bello（安德斯贝略大学物理科学系）
Multi-messenger observations of transient astrophysical sources have the potential to characterize the highest energy accelerators and the most extreme environments in the Universe. Detection of neutrinos, in particular tau neutrinos generated by neutrino oscillations in transit from their sources to Earth, is possible for neutrino energies above 10 PeV using optical Cherenkov detectors imaging upward-moving extensive air showers (EAS). These EAS are produced from Earth interacting tau neutrinos leading to tau leptons that subsequently decay in the atmosphere. We compare neutrino detection sen…
In the last decade, enormous progress has been achieved in the understanding of the various facets of coalescing double neutron star and neutron black hole binary systems. One hopes that the mergers of such compact binaries can be routinely detected with the advanced versions of the ground-based gravitational wave detector facilities, maybe as early as in 2016. From the theoretical side, there has also been mounting evidence that compact binary mergers could be major sources of heavy elements and these ideas have gained recent observational support from the detection of an event that has been …
As a next-generation complex extensive air shower array with a large field of view, the large high altitude air shower observatory (LHAASO) is very sensitive to the very high energy gamma-rays from $\sim$ 300 GeV to 1 PeV, and may thus serve as an important probe for the heavy dark matter (DM) particles. In this study, we make a forecast for the LHAASO sensitivities to the gamma-ray signatures resulting from DM decay in dwarf spheroidal satellite galaxies (dSphs) within the LHAASO field of view. Both individual and combined limits for 19 dSphs incorporating the uncertainties of the DM density …
The rise in the energy spectrum of the positron ratio, observed by the PAMELA satellite above 10 GeV, and other cosmic ray measurements, have been interpreted as a possible signature of Dark Matter annihilation in the Galaxy. However, the large number of free parameters, and the large astrophysical uncertainties, make it difficult to do conclusive statements about the viability of this scenario. Here, we perform a multi-wavelength, multi-messenger analysis, that combines in a consistent way the constraints arising from different astrophysical observations. We show that if standard assumptions …
Microphysics of weakly magnetized relativistic collisionless shock waves, corroborated by recent high performance numerical simulations, indicate the presence of a microturbulent layer of large magnetic field strength behind the shock front, which must decay beyond some hundreds of skin depths. The present paper discusses the dynamics of such microturbulence, borrowing from these same numerical simulations, and calculates the synchrotron signature of a powerlaw of shock accelerated particles. The decaying microturbulent layer is found to leave distinct signatures in the spectro-temporal evolut…
Axions are increasingly favoured as a candidate particle for the dark matter in galaxies, since they satisfy the observational requirements for cold dark matter and are theoretically well motivated. Fluctuations in the axion field give rise to stable localised overdensities known as axion stars, which, for the most massive, compact cases, are potential neutron star mimickers. In principle, there are no fundamental arguments against the multi-messenger observations of GW170817/GRB170817A/AT2017gfo arising from the merger of a neutron star with a neutron star mimicker, rather than from a binary …
We performed the deepest search for an X-ray emission line between 0.5 and 7 keV from non-baryonic dark matter with the Suzaku XIS. Dark matter associated with the Milky Way galaxy was selected as the target to obtain the best signal-to-noise ratio. From the Suzaku archive, we selected 187 data sets of blank sky regions which were dominated by the X-ray diffuse background. The data sets were from 2005 to 2013. Instrumental responses were adjusted by multiple calibration data sets of the Crab Nebula. We also improved the technique of subtracting lines of instrumental origin. These energy spectr…
The recent study on the the 6-year up-going muon neutrinos by the IceCube Collaboration and the multi-messenger analyses support the hypothesis of a two-component scenario explaining the diffuse TeV-PeV neutrino flux. Depending on the steepness of the astrophysical power-law, an excess in the IceCube data is shown in the energy range 10-100 TeV (low-energy excess) or at PeV (high-energy excess). In both cases, we characterize a two-component neutrino flux where decaying Dark Matter particles provide a contribution to the IceCube observations.
We investigate the expected radio emission from short GRBs, guided by the observed distributions of their afterglow parameters. Our motivation is to explore the radio signatures of the forward and reverse shock in a sGRB jet, as well as the off-axis jet component and radio emission from the dynamical ejecta. We estimate the fraction of GRBs detectable in the radio that may be coincident with a GW signal from a neutron star (NS) merger. At the distance to which aLIGO at design specification is sensitive to GWs from NS mergers, we may detect up to 20 % of off-axis jet radio components of these e…
Heavy neutrinos have a long history of consideration in the literature, in particular related to their role as solutions to the problems of neutrino mass, baryon asymmetry, and possibly dark matter. Interestingly, recent developments in the Madala hypothesis, a standard model extension designed to explain persistent LHC lepton anomalies, may also necessitate a heavy neutrino. This prospect is exciting as a dark matter model consisting of a TeV-scale leptophilic fermionic particle is also invoked to explain the electron-positron excess observed by the DAMPE experiment. The tantalising similarit…
A monochromatic line in the cosmic neutrino spectrum would be a smoking gun signature of dark matter. It is intriguing that the IceCube experiment has recently reported two PeV neutrino events with energies that may be equal up to experimental uncertainties, and which have a probability of being a background fluctuation estimated to be less than a percent. Here we explore prospects for these events to be the first indication of a monochromatic line signal from dark matter. While measurable annihilation signatures would seem to be impossible at such energies, we discuss the dark matter quantum …
The precise measurement of cosmic-ray antinuclei serves as an important means for identifying the nature of dark matter and other new astrophysical phenomena, and could be used with other cosmic-ray species to understand cosmic-ray production and propagation in the Galaxy. For instance, low-energy antideuterons would provide a "smoking gun" signature of dark matter annihilation or decay, essentially free of astrophysical background. Studies in recent years have emphasized that models for cosmic-ray antideuterons must be considered together with the abundant cosmic antiprotons and any potential…
Recently, a study has shown that the Bose Einstein Condensates formed by the $d^*$(2380) hexaquarks ($d^*$(2380)-BECs) can be thermally produced in the early universe and they are stable enough to be a competitive candidate of dark matter. Searching for the decaying signature of $d^*$(2380)-BECs is a possible way to verify this dark matter model. In this article, we discuss the scattering and decaying properties of the $d^*$(2380)-BECs and we show that the decay rate of the $d^*$(2380)-BECs is correlated with the TeV cosmic-ray flux. The predicted average decay rate in our Galaxy is several or…
Recent observations by IceCube, notably two PeV cascades accompanied by events at energies ~ (30-400) TeV, are clearly in excess over atmospheric background fluxes and beg for an astroparticle physics explanation. Although some models of astrophysical accelerators can account for the observations within current statistics, intriguing features in the energy and possibly angular distributions of the events make worth exploring alternatives. Here, we entertain the possibility of interpreting the data with a few PeV mass scale decaying Dark Matter, with lifetime of the order of 10^27 s. We discuss…
Since the report of the PeV-TeV neutrinos by the IceCube Collaboration, various particle physics models have been proposed to explain the neutrino spectrum by dark matter particles decaying into neutrinos and other Standard Model particles.In such scenarios, simultaneous $γ$-ray emission is commonly expected. Therefore, multi-messenger connections are generally important for the indirect searches of dark matters. The recent development of $γ$-ray astronomy puts stringent constraints on the properties of dark matter, especially by observations with the Fermi $γ$-ray satellite in the last severa…
The imprint of decaying dark matter (DM) particles in characteristics of the "21 cm fores" -- absorptions in 21 cm from minihalos in spectra of distant radio-loud sources -- is considered within a 1D self-consistent hydrodynamic description of minihalos from their turnaround point to virialization. The most pronounced influence of decaying DM on evolution of minihalos is found in the mass range $M=10^5-10^6\msun$, for which unstable DM with the current upper limit of the ionization rate $ξ_{L} = 0.59\times 10^{-25}$ s$^{-1}$ depresses 21 cm optical depth by an order of magnitude compared to th…
Neutron star (NS) mergers provide us with information rich in physics using multi-messenger astrophysical observations. One of the probable remnants of such a merger is a differentially rotating hot hypermassive neutron star. The stability of the merger remnant depends crucially on the underlying Equation of State (EoS) and thus provides a method to probe the nature of dense matter in NSs. In this work, we search for possible signatures of strangeness containing matter in the NS interior on the secular stability of the merger remnant. We also use recently proposed methods to make a rough estim…
We explore the multi-messenger signatures of encounters between two neutron stars and between a neutron star and a stellar-mass black hole. We focus on the differences between gravitational wave driven binary mergers and dynamical collisions that occur, for example, in globular clusters. For both types of encounters we compare the gravitational wave and neutrino emission properties. We also calculate fallback rates and analyze the properties of the dynamically ejected matter. Last but not least we address the electromagnetic transients that accompany each type of encounter. The canonical nsns …
Emission of relativistic axions from transient sources, such as axion star explosions, can lead to observable signatures. We show that axion bursts from collapsing axion stars can be detectable over the wide range of axion masses $10^{-15} \, \textrm{eV} \lesssim m \lesssim 10^{-7} \, \textrm{eV}$ in laboratory experiments, such as ABRACADABRA, DMRadio and SHAFT. The detection of axion bursts could provide new insights into the fundamental axion potential, which is challenging to probe otherwise. An ensemble of bursts in the distant past would give rise to a diffuse axion background distinct f…
GPS constellation search for exotic physics messengers coincident with the binary neutron star merger GW170817
University of Nevada, Reno（内华达大学里诺分校）；Nevada Bureau of Mines and Geology（内华达矿业与地质局）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）
The `$μ$ from $ν$' supersymmetric standard model ($μν$SSM) solves the $μ$ problem of supersymmetric models and reproduces neutrino data, simply using couplings with the three families of right-handed neutrinos $ν$'s. Novel signatures of supersymmetry at the LHC are expected through these new states, and couplings breaking $R$ parity. All supersymmetric particles are potential candidates for the lightest one, which is not stable leading to prompt or displaced vertices and producing final states with multi-leptons/taus/jets/photons and missing energy. Besides, a decaying gravitino turns out to b…
The background gas humming and multi-messenger transients of stalled supermassive black hole binaries
Universitat Politècnica de València（巴伦西亚理工大学）；Max Planck Institute for Extraterrestrial Physics（马克斯·普朗克地外物理研究所）；Dipartimento di Fisica e Astronomia “Galileo Galilei”, Univ. di Padova（帕多瓦大学伽利略·伽利莱物理与天文学系）；Fesenkov Astrophysical Institute（费森可夫天文物理研究所）
Neutrino and electromagnetic signatures from Superluminous Supernovae: a case study for SN 2017egm
Fermi National Accelerator Laboratory（费米国家加速器实验室）；University of Chicago（芝加哥大学）；Tohoku University（东北大学）；University of Tartu（塔尔图大学）；Columbia University（哥伦比亚大学）；Flatiron Institute（平顿研究所）
The discovery of the compact binary coalescence in both gravitational waves and electromagnetic radiation marks a breakthrough in the field of multi-messenger astronomy and has improved our knowledge in a number of research areas. However, an open question is the exact origin of the observables and if one can confirm reliably that GW170817 and its electromagnetic counterparts resulted from a binary neutron star merger. To answer the question if the observation of GW170817, GRB170817A, and AT2017gfo could be explained by the merger of a neutron star with a black hole, we perform a joint multi-m…
It is shown that a decaying neutralino in a supergravity unified framework is a viable candidate for dark matter. Such a situation arises in the presence of a hidden sector with ultraweak couplings to the visible sector where the neutralino can decay into the hidden sector's lightest supersymmetric particle (LSP) with a lifetime larger than the lifetime of the universe. We present a concrete model where the MSSM/SUGRA is extended to include a hidden sector comprised of $U(1)_{X_1} \times U(1)_{X_2}$ gauge sector and the LSP of the hidden sector is a neutralino which is lighter than the LSP neu…
